June 18, 2013
Climate Change Led To Modern Humans In Stone Age
Lee Rannals for redOrbit.com — Your Universe Online
New evidence suggests that modern humans emerged as the need to find refuge from sudden changes in climate grew.
An international team of researchers found that technological innovation and the emergence of culture and modern behavior took place abruptly. They were able to link these pulses of innovation to the climate that prevailed in sub-Saharan Africa during the Stone Age.
For the past million years, the global climate has varied between glacial periods and interglacial periods, with changes taking place about every 100,000 years. Within these durations there have been periods of abrupt climate change, sometimes happening in the space of a few decades. These changes have been known to affect rainfall in southern Africa.
The team pieced together how rainfall patterns varied in southern Africa over the past 100,000 years by analyzing river delta deposits at the edge of the continent. The ratio of iron to potassium in each of the millimeter layers is a record of the sediment carried by rivers and of the rainfall throughout the whole period.
The researchers' reconstruction of the rainfall over the past 100,000 years shows a series of spikes that took place between 40,000 and 80,000 years ago. These rainfall spikes show levels rose sharply over just a few decades, and fell off again soon afterwards. According to the findings, the climate changes coincided with increases in population, activity and production of technology on the part of our ancestors.
The study helped confirm one of the principal models of Palaeolithic cultural evolution, which correlates technological innovation with the adoption of new refuges and with a resulting increase in population and social networks. Findings revealed that bursts of demographic expansion caused by climate change in southern Africa were key factors in the origin of modern humans' behavior in Africa, and in the dispersal of Homo sapiens.
Scientists reported in February that farming was borrowed from the "Near East" and brought into Europe during this same period. Their findings suggest these people brought domesticated wheat, barley, goats and cattle with them to Europe during the Stone Age.
“[The study] is also useful because it suggests another route across the Black Sea or up the east coast of Bulgaria to the Danube for farmers moving into Europe,” T. Douglas Price, a University of Wisconsin-Madison archaeologist said in a statement. “This contrasts with movement by sea across the Mediterranean or Aegean, which is the standard picture.”